1. Field of the Invention
The present invention relates to a method and apparatus for processing a video signal. More particularly, the invention relates to a method and apparatus for converting a negative video signal to a positive signal, wherein the conversion apparatus receives video signals representative of a negative image, such as a image recorded on a negative film, from image detector such as video camera and converts the video signals to corresponding video signals representative of positive images ready to be viewed on a video monitor.
2. State of the Art
Apparatus for converting photographic pictures, such as motion picture film, to video recordings is well known in the present day state of the art. However, the apparatus, especially low cost models designed for family use, do not have the ability to convert negative photographic film to positive video signals. This is due to the simple fact that there has been no practicable method proposed for the negative-to-positive conversion of video signals in low cost apparatus designed for family use. Professional equipment has been available for negative-to-positive conversion wherein individual components of the composite video signal (i.e. the luminance component and the chrominance component) are separated, and the polarity of each component is reversed by a electronic inverter. The separate, reversed signals are then combined back together to form the composite video signal format. The complexity of the prior art conversion of negative-to-positive signals results in obvious disadvantages. First, the cost is high. Use of apparatus for such negative-to-positive conversion has been limited almost exclusively to photo labs or other professional film developing facilities. Second, each signal processing element in the system inevitably introduces noise and distortions to the signal. The conversion method of the prior art provides no solution to this problem. Third, numerous elements in the conversion systems of the prior art impose higher degrees of difficulties in adjusting the variables involved. Last but not least, the method of the prior art has undesired signal format dependency due to the separation of color difference components. This means a conversion device designed for a
system can not be used on an NTSC system without special modifications and vise versa.
3. Objectives
A principal objective of the invention is to provide a method and apparatus for negative-to-positive conversion of video signals that is simple, effective and low in cost.
A particular objective of the present invention is to provide such a method and apparatus for negative-to-positive conversion that is simple to operate and requires very little adjustment.
Another objective of the present invention is to provide such a method and apparatus for negative-to-positive conversion that can be used independent of signal format.